Source of pictures: pixabay.com
The warm sunlight cast down,giving alethargicfeeling.Thetinyfeet leftfootprints on the beach one after another. The seawatersometimesrushed up to that pair offeetand brought awaysandremainingwithintoes.Macklewashaving a good time at the beach, leaving a happy figure. Thanks toparents'hard-earnedvocation, he could come hereto enjoyarare journey.Due to a rare chance for travelling, his parentsdecided to takehimto the seabecausehewas yearning for it a long time ago.
However,Mackle,asmall "scientist",alreadygota plan in his mind. He intended to "do research". What wouldhe research on? Mackle hada new theme inhisscience class. Theteacher divided the students into groups. Each group shouldfigure outthe cause of a natural phenomenon and doareporttothe whole class. This should not be difficult for Mackle because he knewa lot. However, he wantedto do something differentthis time.He wanted togo into nature,go onfield trips and recorddetailsto doareal "exploration" like a naturalist.This holiday gavehimsuch awonderfulopportunity. The seawaswhathewanted to explorefor a long time. He was especially interested intherise and fallof the tides, whichwas one of the most mysterious natural forces.
Macklerecodedthe time while hisankles were slowly overwhelmed by theflowof the sea.Lookingatthe furthestpart ofthe blue sea, hewas lost in thought: "What is the tide?"
Unexpectedly, thetideis actually controlled by "the sky"! This "sky" refers to the moon and the sun.In fact, the tides arearousedby the sun and the moon, especially the moon.How do these celestial bodiesin the skyaffect the seawateronearth?
Before talkingabout this question, wehave to get straighttwo concepts.Oneis"inertia",another is"universal gravitation". "Inertia"is the force to remaina moving object'soriginal state of motionwhenthe motion state haschanged.For example, when the car makesa turn, we alwaystilttothe opposite directionandfeellikeweare aboutto be thrown out. This iscaused bythe inertia. "Universal gravitation"refers tothemutual forcebetween any two objects.
Let'smove ontothe tide.As we all know,the moon ismoving around the earthwhilethe earth is spinning. The tide is the result of the universal gravitationof themoon(and the sun, whereas the moon plays a greater role) on the earth and the inertiageneratedby the rotational motion of the earth. A forced called as "tidal force" is formed by the combination of the universal gravitation and the inertia. It always pullstheseawaterwithin an areato thedirection ofmoon.People on the ground regard it as therise and fallof the sea. The tide occursataspecific time twice a dayinthe daytimeandatnightrespectively.
Do you think Macklehas figuredoutthis secretof nature?
京公网安备11010502039775号
